In the above co-pending application of Vijai P. Gupta, Ser. No. 476,305 which application is incorporated herein by reference there is described and claimed a method for the preparation of monocarboxylic acid esters of an alkylene glycol monoalkyl ether which comprises reacting at a pot temperature of from about 80.degree. C. to 165.degree. C. a monocarboxylic or halogenated monocarboxylic acid having from 1 to 10 carbon atoms with an alkylene glycol monoalkyl ether having the formulae R(OCH.sub.2 CHR').sub.n OH and ##STR1## wherein R is a straight or branched chain alkyl group containing from 1 to 10 carbon atoms, R' is hydrogen or a methyl group and n is an integer of from 1 to 3, in the presence of an acid catalyst and a water-azeotroping solvent which forms a binary minimum-boiling azeotrope with water within the reaction temperature range. Water is removed via a distillation column during the reaction by azeotropic distillation with the water-azeotroping solvent and the solvent phase and water phase are separated and the solvent phase along with a portion of the water phase returned and refluxed to the overhead section of the distillation column. The desired monocarboxylic acid ester is then recovered and may be used as solvents for inks and coating polymers and in cleansers.
In the preparation of the monocarboxylic acid esters the acid is reacted with an alkylene glycol monoalkyl ether generally in the presence of an inert azeotroping solvent such as toluene with an acid catalyst such as paratoluenesulfonic acid. After about 80 to 95% of the glycol ether and monocarboxylic acid have reacted, the rate of further reaction becomes so low because of equilibrium limitations that the reaction is terminated and the unreacted alkylene glycol monoalkyl ether and monocarboxylic acid, which would be present at between about 10% to 2.5% each in the monocarboxylic acid ester product, are stripped out by distillation. Lower conversion mixtures, e.g. 50% ester, which would, for example, contain 25% monocarboxylic acid and 25% glycol ether, may also be concentrated to an 80-95% ester containing range by a straight distillation prior to employment of the water injection method of the present invention.
The present invention relates to the stripping step and provides a novel method of injecting water into the distillate to provide for a separation and refluxing of an azeotropic solvent to the distillation column during stripping to improve the separation of the unreacted ether and acid reactants.
Applicant is not aware of any truly pertinent prior art that is deemed to be anticipatory or suggestive of the concept of the present invention.